1. Field of the Invention
The present invention generally relates to an image forming device having a resolution compensation function and a method for using the same. More particularly, the present invention relates to an image forming device and a resolution compensation method that adjusts the print quality of scaled printing data by adjusting the resolution of the scaled printing data when scaling the printing data.
2. Description of the Related Art
An image forming device such as a printer or a copier generally prints an original document at real size or prints printing data transmitted from a host computer. A user may want to scale the image size, however, to save paper or to view multiple pages on a single sheet. For example, printing data can be scaled and reduced to print multiple pages on a sheet. This ‘multiple pages on a sheet’ function causes a decrease in the resolution of each page on the printed sheet and a deterioration of the print quality. Likewise, if a copier scales and reduces an original image size, the print quality of the printed image is likely to deteriorate as compared with the original image.
FIG. 1 illustrates a conventional printing method. First, a user creates a document to be printed using a document processing program (APP) 10. The document is transmitted to a graphic device interface (GDI) 20. The GDI 20 is an interface such as those provided by MICROSOFT WINDOWS® operating systems such as WINDOWS® and WINDOWS XP®, and is installed in a host computer together with the operating system. The GDI 20 obtains font, bitmap, and vector information relating to the characters and graphics in the document to be printed and translates the information into function calls recognizable by a driver program 30. Typically, the function calls are referred to as device driver interface (DDI) function calls. When the user gives a print command, the GDI 20 reads resolution information from the driver program 30. The GDI scales the document according to the resolution information and sends the scaled document to the driver program 30.
The driver program 30 receives the function calls from the GDI 20 and converts the calls into printing data recognizable by an image forming device such as a printer 50. The driver program 30 contains resolution information for the document to be printed by the printer 50. Typically, the resolution information is expressed as a number of dots per inch, or dpi. The printing data generated by the driver program 30 is sent to the printer 50 through a spooler 40, and the printer 50 prints the printing data on paper.
The driver program 30 includes a DDI interface 31, a user interface (UI) 32, and a printing data generator 33. The DDI interface 31 translates the function calls received from the GDI 20. The printing data generator 33 converts the function calls into printing data, such as printer control language (PCL) or page description language (PDL), suitable for the printer 50. The printing data is sent to the spooler 40.
The user interface 32 provides the user with an interface for setting the driver program 30 options. Examples of options include print quality, print resolution, and the number of pages per sheet. If the user uses the WINDOWS® operating system, the user can set the print options through a control panel provided by the WINDOWS® operating system. After the user sets the print options, the print options are applied to the print jobs. The WINDOWS® operating system is widely used and is therefore not described in detail for conciseness.
FIG. 2 illustrates the deterioration in detail that occurs in a conventional print method when four pages are printed on a single sheet of paper. If the resolution set in the driver program 30 is 600 dpi, the effective resolution of the printed document A2 is 300 dpi. This is because the 600 dpi image must be printed in one half of the original space, and, thus, one half of the image information is discarded according to the conventional method. As the number of pages per sheet increases, the space available for each page decreases. Accordingly, the effective resolution of the print document A2 is reduced and the print quality of the print document A2 deteriorates.
FIG. 3 illustrates the degradation that occurs when a copier reduces and prints a document at one third of its original size. Referring to FIG. 3, when copying and reducing a document A3 with a preset print resolution of 600 dpi, the printed document A4 is printed in one third of the same space. The image therefore has the same effective resolution as a 200 dpi printout. That is, the reduction of the document A3 causes the degradation of detail in the printed document A4. A facsimile machine, or a multifunction machine which selectively combines the functions of a facsimile machine, a printer, and the like, has similar limitations in scaling an original document.
Accordingly, there is a need for an image forming device with a resolution compensation function that prevents image deterioration when scaling an image.